The invention relates to a diaphragm pump having a pump housing on which a disposable cell is releasably fixable, which disposable cell has a first and a second cell wall which define an operating space between them, and having an operating diaphragm which is drivingly connected to an oscillating stroke drive and which is releasably coupleable with the flexible first cell wall on its diaphragm flat side remote from the stroke drive.
Diaphragm pumps for the conveying and metering of liquids are used in very diverse realizations. High demands are placed on such diaphragm pumps in particular in the case of applications in the health and research sectors.
In order to avoid cross contaminations from various fluids, clean and often sterile fluid paths are mandatory. In order to guarantee the cleanliness and sterility of the fluid paths in the previously known diaphragm pumps, said diaphragm pumps have to be cleaned or even sterilized in an expensive and time-consuming manner. Said cleaning and sterilizing processes often pose great challenges to the users as in particular the expenditure on quality control is linked to enormous expense, effort and uncertainty. The latter has to be constantly monitored by way of additional checks and random sampling and reduced to a minimum. The expense and effort required for cleaning and sterilizing can make the costs connected with the operation of such diaphragm pumps soar. The interruptions in the production or research process generated thereby are unwanted and should be able to be reduced to a minimum.
One efficient method to be able to exchange the fluid-conducting path of a pump system in a short time and at the same time ensure that the entire pump system is clean and, where applicable, even sterile when it is ready for use, is provided by the use of quick change components such as, for example, hoses, fittings and the fluid-conducting components of the pump head of a diaphragm pump.
The market already provides a wide selection of hoses and accessories which are available as disposable components.
EP 0 307 069 B1 has already disclosed a diaphragm pump of the type mentioned in the introduction where the fluid-conducting components of the diaphragm pump are provided in a quick-change disposable or single-use cell. To this end, the disclosed diaphragm pump has a pump housing on which the disposable cell is releasably fixable. Said disposable cell comprises a first and a second cell wall which define an operating space between them. The disclosed diaphragm pump comprises an operating diaphragm which is drivingly connected to an oscillating stroke drive. Said operating diaphragm is releasably coupleable with the flexible first cell wall on its diaphragm flat side remote from the stroke drive. In this case, one of the realizations of the disclosed diaphragm pump shown in EP 0 307 069 B1 provides that the dead space arranged between the operating diaphragm and the first cell wall is connected by means of an outlet line, which is guided right through the operating diaphragm, to a non-return valve arranged outside the diaphragm pump. Said non-return valve does allow air compressed between the operating diaphragm and the first cell wall to flow out, but at the same time prevents air flowing back into the dead space remaining between the operating diaphragm and the first cell wall. Consequently, the first cell wall of the disposable cell and the operating diaphragm are held against one another and coupled together as a result of negative pressure or as a result of adhesive forces. As the outlet line, which is guided through the operating diaphragm and extends up to the non-return valve arranged outside the disclosed diaphragm pump, is comparatively long, a certain residual volume of air always remains in said outlet line which expands again during intake and can pass into the dead space arranged between the operating diaphragm and the first cell wall. As a result, not all the volume generated by the operating diaphragm is sucked into the operating space arranged between the cell walls of the disposable cell, which reduces the efficiency and the accuracy of the diaphragm pump disclosed in EP 0 307 069 B1 and can also result in said diaphragm pump no longer being able to prime itself The capacity of the pump to self-prime is, however, a substantial advantage of diaphragm pumps compared, for example, to centrifugal pumps.
In the case of the diaphragm pump mentioned in the introduction, one of the objects consequently includes creating a diaphragm pump where the dead volume in the dead space between the operating diaphragm and the flexible first cell wall is as small as possible or practically zero.